ACCA is association of chartered accountants.
http://singapore.accaglobal.com/
ACCA qualification is a "professional qualification" and is very
recognised.
An ACCA qualification is like ATPL(Airline transport pilot licence)
for commercial pilots, not sure if it falls under
diploma/degrees
I believe your aim is to be a certified public accountant(CPA).
Taken from here:
http://corp.icpas.org.sg/qualifications/pathway-to-cpa-singapore.aspx
Also from here:
http://www.icpasmembers.org.sg/r_qual.asp?key=nm , you can see ACCA
is one of the recognised professional qualifications for you to
become a certified public accountant in singapore
A diploma may not directly qualify you as an accountant.
Based on
SP's Diploma in accountancy course , You can see from the
website that after completing the diploma, you are only granted
partial exemptions from examinations in ACCA and other professional
bodies
Can't help you much, i have no knowledge about
accountancy
edit: formatting problems